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Closed-loop motor control: An introduction to rotary resolvers and encoders

Is your motor spinning at the intended rate? Closed-loop motor control systems continue to answer this question, as there tends to be a closed-loop system implemented wherever a motor spins. Whether the end system is an automobile (assisted parallel parking with computer controlled steering), a satellite (positions satellite to lock on to a specific signal), or factory floor machinery (a pick-and-place machine), the position feedback sensor is an intrinsic element in the total motor-control system. There are many types of motor control, but this article discusses two that implement an analog signal chain around the position sensor: the resolver and the encoder.

There are two common implementations of rotation/position sensors in a motor-control feedback path: a resolver and an encoder. The feedback path and output signal characteristics of several control systems were evaluated from the analog signal-chain perspective for either a resolver or encoder to ensure signal integrity and optimum performance.